Three major problems are associated with the production and use of metallic nanoparticles. The particles oxidize very readily, which greatly hinders the handling and storage of the material. If the material is stored as a dry powder, the nanoparticles rapidly sinter together. For this reason, the particles are, almost without exception, collected and stored in liquids. The liquid dispersions in turn typically contain surface-active substances, which keep the nanoparticles separate, but which are at the same time impurities that restrict their use. The size of the particles produced also tends to increase, if the production volume is increased.
One known solutions is disclosed in WO publication WO2007/144455, in which metallic nanoparticles are produced continuously by vaporizing metal salts and then reducing using hydrogen. The method is used to manufacture metal nanoparticles, but these are not coated.
Carbon-coated metallic nanoparticles are produced on a small scale using experimental flame reactors. As far as is known, the reactors in question can be used for short periods at a time, due to which the price of the material produced is very high. The particles produced by the combustion process typically also contain a considerable number of impurities, due to an attempt to keep the price of the basic materials low.